/*******************************************************************************
 * Copyright (c) 2009-2011 Luaj.org. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 ******************************************************************************/
package org.luaj.vm2;


/**
 * Upvalue used with Closure formulation
 * <p>
 *
 * @see LuaClosure
 * @see Prototype
 */

public class UpValue {

    LuaValue[] array; // initially the stack, becomes a holder
    int index;

    /**
     * Create an upvalue relative to a stack
     *
     * @param stack the stack
     * @param index the index on the stack for the upvalue
     */
    UpValue(LuaValue[] stack, int index) {
        this.array = stack;
        this.index = index;
    }

    public String toString() {
        return index + "/" + array.length + " " + array[index];
    }

    /**
     * Convert this upvalue to a Java String
     *
     * @return the Java String for this upvalue.
     * @see LuaValue#tojstring()
     */
    public String tojstring() {
        return array[index].tojstring();
    }

    /**
     * Get the value of the upvalue
     *
     * @return the {@link LuaValue} for this upvalue
     */
    public LuaValue getValue() {
        return array[index];
    }

    /**
     * Set the value of the upvalue
     */
    public void setValue(LuaValue value) {
        array[index] = value;
    }

    /**
     * Close this upvalue so it is no longer on the stack
     */
    public void close() {
        LuaValue[] old = array;
        array = new LuaValue[]{old[index]};
        old[index] = null;
        index = 0;
    }
}
